Our conscious memories of daily events (i.e. episodic memory) are made of up countless associations among the many people, places, and things we have experienced over the years. This sort of memory is supported by the hippocampal memory system, also called the medial temporal lobe memory system. The structures that compose the hippocampal memory system, including the hippocampal formation and parahippocampal regions, display remarkable connectional and functional homology between primates and rodents. Thus, rodents provide an excellent animal model for studying human memory. Currently, there is substantial disagreement about how individual structures within the hippocampal and parahippocampal regions are involved in episodic memory. The proposed studies will employ a rat model to examine the contributions of two parahippocampal regions to memory, the postrhinal cortex (POR;rodent homolog to primate parahippocampal cortex) and the perirhinal cortex (PER). POR is thought to be involved in processing spatial/contextual information and PER has an identified role in processing object information. The interactions between the two regions, however, are not well understood. My guiding hypothesis is that the direct connections between the POR and PER provide the neural circuitry for associative representations that link individual items to locations. The specific aims will employ a novel behavioral apparatus to test three key aspects of this hypothesis:1) both the POR and the PER are necessary for associative representations that link objects to places, 2) object-context associations are formed upstream of the hippocampus, and 3) neural correlates of object-context associations will be observed in both PER and POR. Experiments 1 and 2 will employ lesion and inactivation analysis to determine if the PER and POR are necessary for processing 2D visual "objects" and patterned floor backgrounds, respectively, and whether associations that link items and context are formed upstream of the hippocampus. In Experiment 3, single unit activity and local field potentials will be recorded to examine correlates of neural activity in the POR and PER with performance on a task that requires processing of items and contexts. If completed, these experiments will provide greater insight into the role of spatial context in episodic memory, including where context is represented, and how such representations influence other aspects of memory, for example recognition and retrieval. A better understanding of these issues will not only inform our basic understanding of memory, but has the potential to improve treatment of memory impairments associated with brain trauma or disease,e.g. Alzheimer's Disease, epilepsy, and schizophrenia.